ISO 3166 ⇝

country code

Originally country codes were just for countries; but country codes have been allocated for many areas (mostly islands) that aren't countries, such as Antarctica (aq), Christmas Island (cx) and Saint Pierre et Miquelon (pm).

Country codes are defined in ISO 3166 and are used as the top level domain for Internethostnames in most countries but hardly ever in the USA (code "us"). ISO 3166 defines short and full english and french names, two- and three-letter codes and a three-digit code for each country.